In some commercial warewash machines, drain water is at a temperature above that permitted by plumbing codes for draining. This undesired result is due to the fact that cleaning water and rinse water used for cleaning and rinsing in commercial machines are both typically well above the applicable limit temperature. In order to cool the drain water, fresh cold water is sometimes flushed down the drain with the drain water to lower water temperature. A tempering kit is used for this purpose, which allows fresh water to mix with the waste/drain water to bring overall temperature down to the acceptable level before being discharged to the drain. In the operation of these warewash machines, the amount of waste water exiting the machine must also be replenished for by the same amount of incoming replacement fresh water, which must be heated for use in the machine.
Energy efficiency continues to be a significant issue in the field of warewash machines, particularly commercial warewash machines that tend to be high volume machines. It is known to provide heat recovery systems for recovering some heat from drain/waste water that is being purged from the machine as exemplified by U.S. Pat. No. 5,660,193. U.S. Pat. No. 8,146,612 discloses a system in which heat from the drain water is recovered utilizing a counterflow serpentine pipe arrangement.
Nonetheless, it would be desirable to provide a warewash machine with a new and advantageous waste water energy recovery system.